1. Field of the Invention
The present invention relates to a hot melt glue gun with prevention of abnormal melting of a glue stick outside a heating chamber thereof, thereby preventing undesired hardening of the melted glue stick in the solid stick feeding passage and the resultant blockage of the solid stick feeding passage.
2. Description of the Related Art
FIG. 1 of the drawings illustrates a conventional hot melt glue gun comprising a housing 10 having a grip 11. A gas container 12 containing flammable gas is mounted in the grip 11. A combustion chamber 14 is provided in a front portion of the housing 10 and communicated with the gas container 12 via a conduit or gas tube 13. An igniting device 141 is provided to ignite the flammable gas fed into the combustion chamber 14. The heat generated in the combustion chamber 14 is transferred to a heating chamber 17 that is also located in the front portion of the housing 10. The outer wall defining the heating chamber 17 is in direct contact with the outer wall defining the combustion chamber 14 to proceed with heat conduction. A dispensing nozzle 161 is provided at the front end of the housing 10 for dispensing melted glue. A solid glue stick passage is defined in a rear portion of the housing 10 for receiving a solid glue stick 16. A carrier 152 is mounted in the rear portion of the housing 10 and connected to a spring 151 at an end thereof. The carrier 152 comprises a bore that defines a portion of the solid glue stick passage. A sleeve 18 is mounted between the heating chamber 17 and the carrier 152 for holding the solid glue stick 16. When a trigger 15 is pulled, the carrier 152 is actuated to move the solid glue stick 16 into the heating chamber 17. The solid glue stick 16 is melted in the heating chamber 17 and dispensed via the dispensing nozzle 161.
The sleeve 18 is soft and may expand or shrink in diameter in response to a temperature change, thereby accommodating solid glue sticks of various diameters as a result of tolerance. However, the heat from the heating chamber 17 is transferred to the sleeve 18 and thus melts the solid glue stick outside the heating chamber 17 (see bulged portion 162 in FIG. 1). A solid bulged portion 162 is formed after the sleeve 18 is cooled, and the solid glue stick passage is blocked in an end of the sleeve 18. As a result, the solid glue stick 16 cannot be moved, and the user has to remove the solid bulged portion 162 via a fixing hole 19 in the rear portion of the housing 10.
An object of the present invention is to provide a hot melt glue gun with prevention of abnormal melting of the glue stick outside a heating chamber thereof, thereby preventing undesired hardening of the melted glue stick in the solid stick feeding passage and the resultant blockage of the solid stick feeding passage.
In accordance with the present invention, a hot melt glue gun is provided for receiving a solid glue stick, heating the glue stick to its melting point, and dispensing the melted glue. The hot melt glue gun comprises a housing comprising a grip portion and a dispensing nozzle, a heating chamber defined in the housing for heating a solid glue stick to its melting point, means for heating the heating chamber, means for feeding the solid glue stick into the heating chamber, a sleeve for holding a portion of the solid glue stick outside the heating chamber, and insulating means for prohibiting heat transfer from the heating chamber to the sleeve. The insulating means keeps the sleeve at a temperature below the melting point of the solid glue stick, thereby preventing melting of the portion of the solid glue stick outside the heating chamber.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.